Neural prostheses are devices developed for substituting damaged motor, sensory or cognitive functions as a result of injury or disease. Such devices are intended to significantly improve the quality of life for people with disabilities.

The most successful and popular neural prosthesis developed is the cochlear implant. Cochlear implants are small electronic devices that are surgically inserted in cases of severe or complete hearing loss. They use a speech processor and a receiver to convert the sounds captured into electric impulses that directly stimulate the auditory nerve, bypassing the damaged cochlea^[1]. The aim is to reproduce the normal patterns of neural activity at the auditory periphery as accurately as possible. Cochlear implants have shown remarkable restoration of function for patients with hearing disabilities, with users’ hearing test scores matching those of people with normal hearing^[2].

The cochlear implant is an example of how external speech can be converted into internal neural signals. However, the conversion of internal thoughts into external speech in cases of anarthria (total inability to articulate speech) or dysarthria (difficulty speaking) is more complex. This conversion would essentially require a device that can ‘read’ your brain and translate your thoughts into words.

Results recently presented at the Society for Neuroscience annual conference provide promising evidence of brain implant abilities to restore communication by decoding neural activity into words. The brain implants would only require the person to think, unlike the current devices used, which require small movements. Electrodes placed in the patient’s brain can pick up neural signals associated with words and directly convert them into speech with the use of computer programmes. In one study, the device was shown to accurately predict which of eight words a bilingual patient was thinking and could detect both English and Spanish words^[3]. Another patient used the device to successfully produce full sentences, after 15 years of being unable to speak. The patient silently spelled out code words from the NATO phonetic alphabet for letters, which were then organised into words. They ended the session by squeezing their hand together, creating a movement-related neural signal that would disengage the spelling device and disrupt the decoding^[4].

These results demonstrate the brain’s plasticity (ability to modify its connections) in organisation and function, and its ability to recover from injury. Even though more clinical trials are required to improve the current technology and attest its accuracy, the potential benefit of speech neuroprostheses devices in the everyday lives of patients is immense. These devices offer the opportunity for real-time sentence generation to people who previously struggled to communicate with family and friends, dramatically improving their quality of life.

[1] https://www.nidcd.nih.gov/health/cochlear-implants

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3697475/?report=reader

[3] https://www.sciencenews.org/article/brain-implant-reads-peoples-thoughts

[4] https://www.nature.com/articles/s41467-022-33611-3

Edited by Hazel Imrie

Copy-edited by Rachel Shannon